Household refrigerator including defrost control means



March 21, N67 D. w. JACOBUSY y y HOUSEHOLD REFRIGERATOR INCLUDING DEFROST CONTROL MEANS Filed Oct. 18, 1965 2 Sheets-Sheet 1 INVENTOR.

DWKGHT w. IACOBUS 1e 40 BY was TTORMEY March 21, 1967 D. w. JAcoBus gglwgyggy HOUSEHOLD REFRIGERATOR INCLUDING DEFROST CONTROL MEANS Filed Oct. 18, 1965 2 Sheets-Sheet 2 INVENTOR. DWIGHT W. J'ACOBUS Hxs A TORNEY United States Pater 3 ,309,887 Patented Mar. 21, 1967 3,309,887 HOUSEHDLD REFRIGERATOR INCLUDING DEFROST CONTROL MEANS Dwight W. Jacobus, Louisville, Ky., assignor to General Electric Company, a corporation of New York Filed Get. 18, 1965, Ser. No. 496,804 4 Claims. (Cl. 62140) The present invention relates to household refrigerators and is more particularly concerned with a refrigerator of the type including a storage compartment cooled by circulating air from the compartment over an evaporator operating at frosting temperatures and improved means responsive to a change in the pressure drop across the evaporator for initiating the defrost cycle.

Refrigerators including at least one storage compartment, a separate evaporator chamber and fan means for circulating air from the storage compartment over the evaporator are well known. An advantage of such a refrigerator is that the evaporator can be operated normally at below freezing temperatures and can be periodically warmed to defrosting temperatures without significantly disturbing the temperature within the storage compartment. During normal operation of a refrigerator of this type, the accumulation of frost on the evaporator surfaces causes the evaporator air spaces to become increasingly clogged with frost thereby decreasing the air flow through the evaporator and increasing the pressure drop across the evaporator.

An object of the present invention is to provide new and improved defrost control means operable in response to such an increase in the pressure drop for effecting defrost operation of the refrigerator.

A more specific object of the present invention is to provide in a refrigerator of this type, fluid amplifier means operable upon a predetermined increase in the air pressure drop across the evaporator for initiating a defrost cycle.

Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In accordance with the illustrated embodiment of the present invention, there is provided a refrigerator cabinet comprising at least one storage compartment and an evaporator chamber separate from the storage compartment and containing an evaporator operating at frost collecting temperatures. Cooling of the storage compartment is obtained by air circulating means including a fan for withdrawing air from the compartment through the evaporator and discharging cooled air to the compartment. The refrigerator also includes defrost means for periodically removing the frost from the evaporator surfaces. For the purpose of initiating a defrost cycle, there is provided defrost control means including a fluid amplifier having an inlet for receiving air discharged from the fan, a pair of outlets and a control port or ports operable upon a predetermine dincrease in the pressure drop across the evaporator for changing the outlet air flow through the amplifier. Means in one of the outlets responsive to this change in air flow initiates operation of the defrost means.

For a better understanding of the invention reference may be had to the accompanying drawing in which:

FIGURE 1 is a horizontal view partly in section of a household refrigerator embodying the present invention;

FIGURE 2 is a vertical sectional view of a portion of the refrigerator shown in FIGURE 1 taken generally along line 2-2 of FIGURE 1; and

FIGURE 3 is a wiring diagram of a suitable control circuit for controlling the operation of the refrigerator of FIGURE 1.

The illustrated refrigerator comprises insulated walls defining a freezer compartment 1 intended to operate at a temperature below freezing and a fresh food compartment 2 adapted to operate at a temperature above freezing as, for example, 35 to 40 F. The two compartments are separated by a horizontal insulating partition 3 which also includes means for supplying refrigerated air to the two compartments in the form of an evaporator chamber 4 containing an evaporator 5, and a fan 6 for circulating air from the compartments 1 and 2 through the chamber 4. More specifically, air is withdrawn from the freezer compartment 1 through a passage 8 connecting the freezer compartment 1 with the inlet or front end of the chamber 4 and refrigerated air is supplied to the freezer compartment through an air passage -9. Air is withdrawn from the fresh food compartment 2 through a passage 10 and refrigerated air is supplied to the fresh food compartment by means of a passage 11 extending through the bottom of the partition 3. The refrigerator also comprises a refrigerant condensing means including a compressor 12 (FIGURE 3) for supplying liquid refrigerant to the evaporator 5.

The illustrated evaporator 5 comprises a plurality of refrigerant tubes or passes 14 and a plurality of fins 15 extending transversely of the passes 14 in a direction generally parallel to the direction of air flow through the evaporator chamber 4. During normal refrigerating operation of the refrigerator, the evaporator 5 operates at below freezing temperatures in order to supply the freezer compartment 1 with air cooled to such temperatures. Moisture contained in the circulating air from the two compartments, particularly from the above freezing compartment 2, deposits on the evaporator surfaces in the form of frost. The frost not only insulates the evaporator surfaces but also blocks or clogs the air passages between the fins 15 and restrict the passage of air through the evaporator structure. Accordingly, it is necessary to periodically warm the evaporator 5 to above freezing temperatures for the purpose of removing this layer of frost.

Various evaporator warming means are well known. In the illustrated embodiment of the present invention, defrosting of the evaporator is effected by means of a radiant heater 16 extending transversely of the evaporator. Energization of the radiant heater 16 during the defrost cycle, warms all the surfaces of the evaporator to temperatures such that the frost is melted. The defrost Water collects on a drain pan 17 and is discharged by suitable drain means (not shown) to a point outside of the storage compartments 1 and 2.

As the passages between the fins 15 become more and more constricted by the deposit of frost on the fin surfaces during the normal or refrigerating cycles of operation, the air pressure drop across or through the evaporator increases in proportion to the frost load. In accordance with the present invention means responsive to this increased pressure differential are provided for interrupting the normal cycles of operation of the refrigerator and initiating the defrost cycle. Specifically there is provided a fluid amplifier generally indicated by the numeral 21 configurated to normally exit air passing therethrough through one of two outlets and to divert this air flow to the other exit when the pressure drop across the evaporator resulting from a frost load on the evaporator reaches a predetermined maximum. This fluid amplifier, shown particularly in FIGURE 1 of the drawing, comprises an air inlet 21 for receiving a portion of the air from the discharge side of the fan 6, that is relatively high pressure air, a first or normal flow outlet 22 communicating with a portion of the chamber 4 on the upstream or low presa sure side of the fan 6 and a second outlet 23 which also communicates with this low pressure portion of the chamber 4. In accordance with the usual fluid amplifier practice, the fluid amplifier also includes control port means for controlling the flow of air through one or the other of the two outlets 22 and 23. In the illustrated embodiment of the invention, there is provided a first control port 25 communicating with the chamber 4 between the evaporator 5 and the fan 6 and a second control port 26 communicating with the inlet end 27 of the chamber 4, that is, a point upstream from the evaporator 5. The entire fluid amplifier structure may, if desired, :be formed within a body of rigid foam insulation 29 within the partition 3.

A fluid amplifier has the ability to switch an air stream from one outlet to the other as a function of the pressure difference at its control ports. As the frost load on the evaporator 5 increases during normal operation of the refrigerator, the resultant increase in resistance to air flow through the evaporator will cause an increased pressure differential between the inlet or upstream portion 27 of the evaporator and the downstream portion between the evaporator 5 and the fan 6. The fluid amplifier is so designed that under the pressure conditions existing when there is no frost or an acceptable amount of frost on the evaporator surfaces, air flowing through the fluid amplifier will exit through the outlet 22 whereas when the frost load reaches a predetermined maximum, the resultant increased differential in pressure at the control ports 25 and 26 will cause a switching of all or a portion of the air flow through .the fluid amplifier to the outlet 23, this switch or change in air flow can be employed to initiate a defrost cycle.

Means actuated by this change in air flow are provided for initiating a defrost cycle. In the illustrated embodiment of the invention, this means comprises a thermostat 30 positioned in one wall of the fluid amplifier outlet 23. Under low frost load conditions, no air flows through outlet 23 so that the thermostat 30 is not directly subjected to the below freezing air temperatures of the circulating air. However, when an increased pressure differential across the evaporator 5 diverts the air flow within the fluid amplifier to the outlet 23, the cold air stream contacting the thermostat 30 lowers its temperature to a point such that a defrost control switch forming part of, or operated by the thermostat 30, initiates a defrost cycle.

Suitable control circuitry for controlling the normal and defrost operation of the refrigerator is illustrated in FIGURE 3 of the drawing includes the thermostat 30 actuating switch means 31 connected across the supply lines 33 and 34 through a temperature controlled thermostat 35 positioned at some point within the fresh food compartment 2 so as to be responsive to the temperature therein. Switch means 31 is of the double throw type including a first contact 36 which is normally engaged by the switch arm 37 to complete a circuit energizing both the fan 6 and the compressor 12 when the thermostat 35 calls for cooling. When the frost load on the evaporator 5 increases to a point at which the thermostat 30 is cooled by the refrigerated air flow diverted to the outlet passage 23, switch arm 31 is moved into engagement with the second contact 39 thereby opening the circuit to the fan motor 6 and the compressor 12 and closing a circuit including the defrost heater 16 with the result that the evaporator 5 is warmed to defrosting temperatures by the heater 16. If desired, a defrost terminating switch 40 responsive to the temperature of the evaporator 5 may be employed to open this circuit including the defrost heater after the evaporator temperature has reached a point above freezing. Alternatively, the thermostat 30 may be positioned sufficiently close to the terminal end of the outlet 23 so as to be warmed by the radiant heater during the defrost cycle to a reset temperature in which the heater 16 is de-energized and the fan 6 and compressor 12 are again connected across the supply lines 33 and 34 through the temperature control thermostat 35.

It will be understood that the invention is not limited to the specific fluid amplifier illustrated in the drawing and that other well known types utilizing one or more control ports or jets adapted to control a main fluid flow between one of several outlet passages in response to an increased pressure difierential across the evaporator 5 may be employed. Also, the warming of the evaporator 5 to defrosting temperatures may be effected by defrost means other than the radiant heater 16, such means including, for example, well known hot gas defrosting involving the flow of hot compressed refrigerant through the passes 14. Means other than a temperature responsive thermostat may be employed to initiate and control the defrost cycle. For example, means actuated by a change in the velocity of air flow through one or the other of the amplifier outlets may be used to actuate the switch arm 31.

Therefore while there has been shown and described a particular embodiment of the invention, it is to be understood that it is not limited thereto and is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A refrigerator comprising a storage compartment, an evaporator chamber containing an evaporator operating at frost collecting temperatures, an air circulating means including a fan for circulating a stream of air from said compartment through said chamber and evaporator and back to said compartment, and defrost means for periodically defrosting said evaporator; the improvement comprising:

means for controlling operation of said defrost means including a fluid amplifier having an inlet for receiving air discharged from said fan, and first and second outlets communicating with a lower pressure point in said air stream ahead of said fan,

said amplifier including control port means operable in response to a pressure change in said air stream for changing the flow of air from said first outlet to said second outlet, and

means in one of said outlets responsive to said change for controlling the operation of said defrost means.

2. A refrigerator comprising a storage compartment, an evaporator chamber containing an evaporator operating at frost collecting temperatures, an air circulating means including a fan for withdrawing air from. said compartment throuh said chamber and evaporator and discharging higher pressure cooled air to said compartment, and defrost means for periodicaly defrosting said evaporator; the improvement comprising:

means for controlling operation of said defrost means including a fluid amplifier having an inlet for receiving air discharged from said fan, and first and second outlets communicating with a lower pressure point in said air stream ahead of said fan,

said amplifier including control port means operable in response to an increase in the air pressure drop across said evaporator for changing the flow of air from said first outlet to said second outlet, and means in one of said outlets responsive to said change for controlling the operation of said defrost means.

3. A refrigerator comprising a storage compartment, an evaporator chamber containing an evaporator operating at frost collecting temperatures, an air circulating means including a fan for withdrawing air from said compartment through said chamber and evaporator and discharging higher pressure cooled air to said compartment, and defrost means for periodically defrosting said evaporator; the improvement comprising:

means for controlling operation of said defrost means including a fluid amplifier having an inlet for receiving air discharged from said fan, and first and second outlets communicating with the outlet portion of said chamber between said evaporator and said fan, said amplifier including a first and second control port respectively communicating With said chamber upstream and downstream from said evaporator and operable in response to an increase in the air pressure drop across said evaporator for changing the flow of air from said first outlet to said second outlet, and means in one of said outlets responsive to said change for controlling the operation of said defrost means. 4. A refrigerator comprising a freezer compartment and a fresh food storage compartment, an evaporator chamber containing an evaporator operating at frost collecting temperatures, an air circulating means including a propeller type fan for withdrawing air from said compartments through said chamber and evaporator and discharging higher pressure cooled air to said compartments and defrost means for periodicaly defrosting said evaporator; the improvement comprising:

means for controlling operation of said defrost means including a fluid amplifier having an inlet for remeans in one of said outlets responsive to said change for controlling the operation of said defrost means.

References Cited by the Examiner UNITED STATES PATENTS 2,728,197 1 2/ 195 5 Ellenberger 62P-140' 2,97 5,611 3 1961 Pietsch 6 2-140 3,004,399 10/1961 Keller 6 2l51 3,107,499 10/ 1963 Iokela 6214O MEYER PERLIN Primarv Examiner. 

1. A REFRIGERATOR COMPRISING A STORAGE COMPARTMENT, AN EVAPORATOR CHAMBER CONTAINING AN EVAPORATOR OPERATING AT FROST COLLECTING TEMPERATURES, AN AIR CIRCULATING MEANS INCLUDING A FAN FOR CIRCULATING A STREAM OF AIR FROM SAID COMPARTMENT THROUGH SAID CHAMBER AND EVAPORATOR AND BACK TO SAID COMPARTMENT, AND DEFROST MEANS FOR PERIODICALLY DEFROSTING SAID EVAPORATOR; THE IMPROVEMENT COMPRISING: MEANS FOR CONTROLLING OPERATION OF SAID DEFROST MEANS INCLUDING A FLUID AMPLIFIER HAVING AN INLET FOR RECEIVING AIR DISCHARGED FROM SAID FAN, AND FIRST AND SECOND OUTLETS COMMUNICATING WITH A LOWER PRESSURE POINT IN SAID AIR STREAM AHEAD OF SAID FAN, 